Lifting arm



FIG. 1 is a right side view of a lifting arm showing the claimed design;

FIG. 2 is a front perspective view thereof;

FIG. 3 is a rear perspective view thereof;

FIG. 4 is another right side view thereof, in an environment in which itmay be used; and,

FIG. 5 is a rear view thereof.

The broken lines in the figures show portions of the lifting arm andenvironment that form no part of the claimed design.

Portions of the lifting arm that are not shown form no part of theclaimed design.

CLAIM The ornamental design for a lifting arm, as shown and described.